JOHANNESBURG, South Africa — Bishop Desmond Tutu, reacting to President Reagan's speech on South Africa, called it "utterly racist and totally disgusting" and declared angrily, "The West, as far as I am concerned, can go to hell."

Tutu predicted that bitter, disillusioned blacks would increasingly turn away from peaceful protests, now that the United States and its allies have deprived them of the political leverage of international economic sanctions, and the result would be even greater violence and perhaps the racial civil war he has long warned against.

Tutu charged that Reagan, as well as British Prime Minister Margaret Thatcher and West German Chancellor Helmut Kohl, are in effect telling South Africa's 25 million blacks that "we are completely dispensable and can forget about help from them."

'Quite Angry,' Bishop Says

"I am quite angry," said the black Anglican prelate, the 1984 Nobel Peace laureate for his long years of anti-apartheid campaigning, from his home in Soweto, the black satellite city outside Johannesburg. "And so, let me say it again--the West can go to hell."

Tutu said he found Reagan's speech, broadcast here by the Voice of America and later in a censored version by state-run South Africa television, "ill-informed, stupid, contradictory and nauseating."

President Pieter W. Botha "must be overjoyed that he has such a wonderful public relations officer in the White House--he could not have written a better speech himself," Tutu complained.

The embattled South African government welcomed the Reagan speech, particularly the U.S. recognition of its efforts at step-by-step political reforms and the President's condemnation of the outlawed African National Congress' use of violence to bring apartheid to an end.

"The South African government welcomes President Reagan's stand that it is under no compulsion to negotiate the future of the country with an organization that proposes a Communist regime and that uses terrorism to bring this about," Foreign Minister Roelof F. (Pik) Botha said in a statement Tuesday night.

Regime Applauds Reagan

"It is encouraging that President Reagan acknowledges the dramatic changes brought about under the leadership of President Botha. It is also encouraging that President Reagan underlines the fact that South Africa's problems are complex and that solutions should not be transplanted from outside."

But the foreign minister expressed his government's "regret" over Reagan's sharp criticism of the state of emergency imposed June 12 and said the the harsh measures were necessary. "Only in a climate where violence and intimidation are absent," he said, could the country's political reforms proceed.

The Reagan speech was widely seen here as mostly sympathetic to the Pretoria government and intended to ease international pressures on South Africa, thus giving it a bit more time to pursue reforms in its own way and at its own pace.

"Reagan has moved significantly closer to P. W. Botha's position," said Professor Carl F. Noffke, director of Rand Afrikaans University's American Studies Institute. "This speech will help a lot in preventing the wholesale imposition of sanctions on us. That onslaught would probably drive us into such a defensive posture that the reforms would inevitably be put aside.

Buying Time

"Reagan has not only bought us more time for reform, but at a considerable political risk to himself has tried to end the siege mentality that has been building in South Africa," Noffke said. "I would hope that we will have the confidence now to proceed with reforms and to take a more realistic approach to major Western countries that are concerned about developments here."

John Wilson, president of the influential Federated Chamber of Industries, also welcomed Reagan's speech for its "note of realism . . . that neither punitive economic sanctions nor a retreat into isolation will assist South Africa to develop a new, just, stable society with an economic, political and cultural system open to all.

"The Federated Chamber of Industries associates itself with President Reagan's call for an explicit timetable for meaningful political dialogue, initiated through the release of political leaders and permitting normal democratic processes to take place in the country," Wilson said.

But Prof. John Barratt, director of the South African Institute of International Relations, said he felt the government was more likely to take comfort from Reagan's words of praise and to ignore his criticism.

"However sharp Reagan may have been in denouncing apartheid and the state of emergency, what will be noticed here are his even stronger expressions of support for the reforms and of understanding for the government's position," Barratt added.